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authorStefan Hajnoczi <stefanha@redhat.com>2018-03-07 14:42:05 +0000
committerStefan Hajnoczi <stefanha@redhat.com>2018-03-08 17:38:51 +0000
commit4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 (patch)
tree629e62ffd260635269f0fdcedd392256639c09cc /cpus.c
parent184b9623461e73ef79f5cebe68bdbcf2e4751e22 (diff)
vl: introduce vm_shutdown()
Commit 00d09fdbbae5f7864ce754913efc84c12fdf9f1a ("vl: pause vcpus before stopping iothreads") and commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") tried to work around the fact that emulation was still active during termination by stopping iothreads. They suffer from race conditions: 1. virtio_scsi_handle_cmd_vq() racing with iothread_stop_all() hits the virtio_scsi_ctx_check() assertion failure because the BDS AioContext has been modified by iothread_stop_all(). 2. Guest vq kick racing with main loop termination leaves a readable ioeventfd that is handled by the next aio_poll() when external clients are enabled again, resulting in unwanted emulation activity. This patch obsoletes those commits by fully disabling emulation activity when vcpus are stopped. Use the new vm_shutdown() function instead of pause_all_vcpus() so that vm change state handlers are invoked too. Virtio devices will now stop their ioeventfds, preventing further emulation activity after vm_stop(). Note that vm_stop(RUN_STATE_SHUTDOWN) cannot be used because it emits a QMP STOP event that may affect existing clients. It is no longer necessary to call replay_disable_events() directly since vm_shutdown() does so already. Drop iothread_stop_all() since it is no longer used. Cc: Fam Zheng <famz@redhat.com> Cc: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20180307144205.20619-5-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'cpus.c')
-rw-r--r--cpus.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/cpus.c b/cpus.c
index 9bcff7d63c..d8fe90eafe 100644
--- a/cpus.c
+++ b/cpus.c
@@ -993,7 +993,7 @@ void cpu_synchronize_all_pre_loadvm(void)
}
}
-static int do_vm_stop(RunState state)
+static int do_vm_stop(RunState state, bool send_stop)
{
int ret = 0;
@@ -1002,7 +1002,9 @@ static int do_vm_stop(RunState state)
pause_all_vcpus();
runstate_set(state);
vm_state_notify(0, state);
- qapi_event_send_stop(&error_abort);
+ if (send_stop) {
+ qapi_event_send_stop(&error_abort);
+ }
}
bdrv_drain_all();
@@ -1012,6 +1014,14 @@ static int do_vm_stop(RunState state)
return ret;
}
+/* Special vm_stop() variant for terminating the process. Historically clients
+ * did not expect a QMP STOP event and so we need to retain compatibility.
+ */
+int vm_shutdown(void)
+{
+ return do_vm_stop(RUN_STATE_SHUTDOWN, false);
+}
+
static bool cpu_can_run(CPUState *cpu)
{
if (cpu->stop) {
@@ -1994,7 +2004,7 @@ int vm_stop(RunState state)
return 0;
}
- return do_vm_stop(state);
+ return do_vm_stop(state, true);
}
/**